Spinal implant system

ABSTRACT

A spinal implant system including components designed to be affixed to the spinal column. The system includes spinal rods, attachment devices, and interpositional sleeves for securing the attachment devices to the rods. The attachment devices may be various types of spinal hooks, screws, couplers, rod connectors, clamps, or other such devices.

BACKGROUND OF THE INVENTION

The present invention relates to a spinal implant system, and issuitable for use in treatments for correcting various spinaldeformities. In particular, this invention relates to a spinal system ofthe type that includes an interpositional sleeve for securing varioustypes of attachment devices to a spinal rod.

The use of an interpositional sleeve to secure a spinal attachmentdevice to a rod is taught in the prior art, such as in U.S. Pat. Nos.5,112,332 and 5,116,334 to Cozad et al. The present invention is amodification and improvement of these Cozad et al. patents, and as suchthese two U.S. Pat. Nos. 5,112,332 and 5,116,334, are incorporatedherein by reference. Both of these Cozad et al. patents, as well as thepresent invention, are assigned to Zimmer, Inc. These two Cozad et al.patents are both divisional of U.S. Pat. No. 5,074,864 to Cozad et al.

These Cozad et al. patents disclose a spinal implant system whichincludes a tapered split sleeve having a separate, discrete lock memberor lock nut securable over the sleeve. The lock member interacts withthe open back attachment device by acting on an exterior surface of theattachment device to secure an interference frictional interconnectionbetween the tapered sleeve and the attachment device to secure thedevice to the rod.

The following other spinal systems are known which disclose the use ofan interpositional sleeve:

U.S. Pat. No. 5,010,879 to Moriya et al. discloses a spinal systemhaving a wedge-like slit sleeve having a cylindrical body with a flange7a on one end and a tapered portion 8a on the other end. The wedge-likemember is forcibly inserted at the tapered end thereof between a spinalhook and a rod.

U.S. Pat. Nos. 4,815,453 and 4,641,636 to Cotrel disclose a spinalsystem which includes a sleeve 30 having a conical part 31. A pressurescrew 25 is provided to selectively fix the anchoring members inposition on the spinal rod or pin, which has a roughened surface.

U.S. Pat. No. 4,404,967 to Bacal et al. discloses a spinal system havinga split or cut sleeve 3 with skew recesses 4 made along the cut. Theinner surfaces of recesses 4 constitute bearing surfaces for a pin 2which protrudes from the spinal rod 1. A conical end of the sleeve fitsinto a corresponding recess in the hook.

U.S. Pat. No. 4,269,178 to Keene discloses an open back spinal hookhaving a sleeve which is slidable along the spinal rod and into thehook. A lock nut may then be used to secure the position of the sleeve.

OBJECTS OF THE INVENTION

A principal object of this invention is to provide a spinal implantsystem with a secure attachment mechanism that is easy to use, buteffective.

Another object of the invention is to provide an interpositional sleevethat can be inserted between a spinal attachment device and a spinal rodto secure the attachment device to the rod without the need for anyadditional separate locking member, and thus with the securing featuresbuilt integrally into the features of the sleeve and attachment devicethemselves.

A further object of the invention is to provide such an interpositionalspinal sleeve with a first taper and a second reverse taper, such thatthe narrow ends of each taper converge to enable the sleeve to beremoved from the attachment device, if necessary.

A still further object of the invention is to provide an attachmentdevice which provides a first position for partially seating the sleeve,plus a second position for fully seating the sleeve member between therod and the attachment device.

An additional object of the invention is to provide a sleeve forpositioning between a rod and an attachment device, wherein the sleevecan snap fit laterally onto the rod, rather than have to slide thesleeve onto the rod from one of the ends of the rod to the desiredposition.

SUMMARY OF THE INVENTION

The present invention provides a spinal implant system includingcomponents designed to be affixed to the spinal column. The systemincludes spinal rods, attachment devices, and interpositional sleevesfor securing the attachment devices to the rods. The attachment devicesmay be various types of spinal hooks, screws, couplers, rod connectors,clamps or other such devices. The attachment device provides twodiscrete positions for positioning the sleeve, a first partially seatedposition and a second fully seated position. The sleeve canadvantageously be snap fit onto the rod in the desired location. Inaddition, the sleeve has a first taper and a second reverse taper withthe narrow ends of each taper converging to form a reduced portion. Thereduced portion may further include a recessed transition zone. Thespinal implant system of the present invention provides a stable andsecure way to fix the position of a spinal attachment device onto aspinal rod.

BRIEF DESCRIPTION OF THE DRAWINGS

These features and objects of the invention, as well as others, willbecome apparent to those skilled in the art by referring to theaccompanying drawings:

FIG. 1 is a perspective view of a rod, an attachment device, and aninterpositional sleeve according to the present spinal implant systeminvention, and shown prior to insertion of the sleeve in the attachmentdevice;

FIG. 2 is a perspective view of the components of FIG. 1 with the sleeveshown in the first partially seated position in the attachment device;

FIG. 3 is a perspective view of the components of FIG. 1 with the sleeveshown in the second fully seated position in the attachment device;

FIG. 4 is a perspective view of the sleeve of FIG. 1;

FIG. 5 is a perspective view of the sleeve of FIG. 4 shown from theopposite end;

FIG. 6 is a bottom view of the sleeve of FIG. 4;

FIG. 7 is a top view of the sleeve of FIG. 4;

FIG. 8 is a perspective view of the attachment device of FIG. 1;

FIG. 9 is a top view of the attachment device of FIG. 8;

FIG. 10 is a cross-sectional view taken along lines 10--10 of FIG. 9;

FIG. 11 is a cross-sectional view taken along lines 11--11 of FIG. 8;and

FIG. 12 is an end view of the attachment device of FIG. 8 as viewed fromlines 12--12 of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-12 illustrate a particularly advantageous embodiment of a spinalimplant system according to the present invention. The spinal implantsystem includes a spinal rod 1, an attachment device 40, and aninterpositional sleeve 10 for securing the device 40 to rod 1. Theattachment device 40 may be one of various types of spinal hooks,screws, couplers, rod connectors, clamps, or other such devices. Thepresent invention is illustrated with the attachment device as a spinalhook with extending hook portion 49; however, it is understood that anysuitable attachment device may be utilized in accordance with thepresent invention.

It is understood in keeping with spinal surgery techniques that aplurality of spinal rods can be used, each with a plurality of spinalattachment devices affixed thereto. The attachment devices may either beused to affix the rods to the spinal column or to affix the position oftwo rods with respect to each other.

The attachment device 40 includes a first position for partially seatingthe sleeve 10 between the rod 1 and the attachment device 40, as shownin FIG. 2, and a second position for fully seating the sleeve 10, asshown in FIG. 3.

FIG. 1 shows the sleeve 10 prior to insertion in device 40. The sleeve10 is positioned on the rod 1, while the attachment device 40 is held inposition by a suitable hook holder instrument (not shown). Such hookholder instruments are known in the art and grip the attachment device40 via recessed gripping holes 48. Then a suitable pusher or crunchertype instrument (not shown) can be used to insert the sleeve 10 intoattachment device 40 by applying pressure on one side of sleeve 10 andon the opposite side of attachment device 40 to bring the sleeve to thepartially seated position of FIG. 2. This partially seated positionattaches the sleeve 10 to device 40 about rod 1, and yet allows thesleeve 10/device 40 assembly to still slide along rod 1 to allowadjustment of their position along rod 1. Then a further suitablecincher-type instrument (not shown) is used to apply pressure to the oneside of sleeve 10 and the opposite side of device 40 to bring thesecomponents together into the fully seated position of FIG. 3. This fullyseated position locks or secures the attachment device 40 onto rod 1.Final locking of the attachment device 40 and the sleeve 10 to the rod1, and thus final component fixation is obtained by the interference fitof the sleeve 10 between both the attachment device 10 and rod 1 at thisfully seated position. It is noted that when the sleeve 10 is fullyseated in the attachment device 40, the length of the sleeve (LS) ispreferably fully contained within the length of the attachment device(LA).

The elongated spinal rod 1 may be any suitable length or any suitablediameter (D). The cylindrical rod 1 has a smooth outer surface. Thesleeve 10 has a longitudinal cylindrical bore 16 therethrough forfitting about rod 1. The surface of the bore 16 is also smooth.

The sleeve 10 includes a first portion 15 and a second portion 25. Thesecond portion is relatively shorter than the first portion. The firstportion 15 includes a first outer taper 11 with a wide end 13 taperingto a narrow end 12. The second portion 25 includes a second outerreverse taper 21 with a narrow end 22 tapering to a wide end 23. Thenarrow end 12 of first taper 11 converges with the narrow end 22 ofsecond taper 21 forming a reduced or narrowed portion. A recessedtransition zone or groove 29 may be provided between the first andsecond tapers 11 and 21. The recessed transition zone 29 of sleeve 10aligns with the edge 44 of counterbore 45 of device 40 when the sleeve10 is fully seated therein. Thus, neither taper 11 or 21 of sleeve 10 isproviding a line contact. The reverse taper 21 helps provide a lockingposition when the sleeve 10 is pushed to its fully seated position withthe second portion 25 of sleeve 10 located in counterbore 45 ofattachment device 40. This dual taper design provides an audible andforce-feel feedback to the surgeon to communicate a positive lock of thesleeve 10 in the fully seated position in device 40. The reverse taper21 of the sleeve 10 also allows the sleeve to be unlocked from theattachment device 40 with a suitable instrument (not shown) shouldremoval of the sleeve 10 be necessary. The reverse taper 21 allowssleeve 10 to slide over the edge 44 of counterbore 45 in attachmentdevice 40 facilitating such removal (as opposed to a sharp edge such asa 90 degree flange which would catch on edge 44 to resist removal). Thecounterbore 45 provides a retaining wall 55 to help lock dual tapersleeve 10 into its fully seated position.

The attachment device 40 includes an inner taper 51 having a wide end 53tapering to a narrow end 54. A chamfer 52 extends from the wide end 53of inner taper 51. The counterbore 45 is positioned at the narrow end 54of taper 51 forming retaining wall 55 therebetween. When the sleeve 10is positioned and fully seated between rod 1 and device 40, the firstouter taper 11 mates with the inner taper 51 of device 40. The secondportion 25 of sleeve 10 mates with counterbore 45 to secure device 40 torod 1.

The sleeve 10 has an open back 17 extending the length (LS) of thesleeve 10. The open back 17 interconnects with bore 16. The attachmentdevice 40 has an open back 57 extending the length (LA) of theattachment device 40. The open back of device 40 interconnects withinner taper 51 and counterbore 45. The open back 57 of device 40 allowsrod 1 to easily drop into position. The open back 17 of the sleeve 10has a width (WS), while the open back of the attachment device has awidth (WA). The counterbore 45 includes a semicircular bottom wall 46which extends into oppositely located straight side walls 47. Thecounterbore 45 between side walls 47 has a width (WC). The width (WC) ofcounterbore 45 is larger than the width (WA) of attachment device 40.

The second portion 25 of sleeve 10 includes a tapered rounded bottomsurface 24 forming the second outer reverse taper 21 and two relief cuts28 on opposite sides of second portion 25 forming two legs 26 extendingfrom bottom surface 24. The depth of the relief cuts 28 can vary. Theserelief cuts 28 help give clearance to allow sleeve 10 to enter the taper51 of attachment device 40. A retainment tab 27 extends from each leg26. The retainment tabs 27 allow the sleeve 10 to maintain properalignment within the attachment device. These retainment tabs helpprevent rotation of sleeve 10 within attachment device 40, thus actingas antirotation tabs. The tabs 27 help engage the sleeve in theattachment device 40 in both the partially seated and fully seatedpositions. The retainment tabs 27 extend above the two longitudinalspaced upper edges 31 on either side of open back 17 of sleeve 10. Achamfer 18 extends from each upper edge 31 of sleeve 10 to alongitudinal lower edge 32. It is the distance between spaced loweredges 32 which creates the width (WS) of the open back 17 of sleeve 10.The distance between the upper edges 31 would be wider than width (WS)as the chamfer 18 extends outwardly from lower edges 32 to upper edges31. The included angle between the two angled chamfered surfaces isabout 60 degrees. The width (WS) of sleeve 10 is sufficient to enablethe sleeve 10 to snap fit laterally onto rod 1 and laterally retainsleeve 10 on rod 1. The rod 1 has a diameter (D). The width (WS) of theopen back 17 of sleeve 10 is slightly smaller than the diameter (D) ofrod 1, but is large enough to snap fit laterally onto rod 1. The sleeve10 can be snapped back off the rod, if needed. The ability to snap fitthe sleeve 10 onto rod 1 allows the sleeve 10 to be easily positioned atthe desired location on rod 1. While the sleeve 10 can still be slidonto the rod 1 from an end of the rod, the ability to snap the sleeveonto the rod laterally at any desired location along the rod 1 providesmore versatility than designs in which the sleeve 10 has to be slid froman end of the rod 1.

The retainment tabs 27 each include an abutting tab face 37 to abutagainst retaining wall 55 of counterbore 45. This abutting relationshiphelps secure the sleeve 10 in the counterbore 45 of attachment device40, and thus secure the sleeve 10 and attachment device to rod 1 in itsfully seated position. When the sleeve 10 is fully seated in theattachment device 40, the bore 16 of sleeve 10 is frictionally retainedon cylindrical rod 1, while the taper 51 of attachment device 40 isfrictionally secured on first sleeve taper 11 with the second portion 25of sleeve 10 secured and retained via the second reverse taper 21 andretainment tabs 27 in counterbore 45. The open back 17 of sleeve 10enables the sleeve 10 to be compressed between the rod 1 and device 40to create a secure friction fit therebetween. Thus, retention of theattachment device 40 and sleeve 10 to the rod 1 is accomplished by thelocking of tapers 11 and 51 and the mechanical resistance of the secondportion 25 or locking hub in the counterbore 45.

The upper longitudinal spaced edges 61 of device 40 created by the openback 57 include two oppositely located recessed cuts 58. These recessedcuts provide a locating position for accepting retainment tabs 27therein to provide the partially seated position of FIG. 2. Thus, theopen back 57 of device 40 enables sleeve 10 to be maintained in apartially seated position via the interconnection of recessed cuts 58and tabs 27. The retainment tabs 27 each include a tapered leading edge35. This tapered leading edge 35 helps allow the retainment tab to slideout of recessed cuts 58 in order to move the sleeve from the partiallyseated position to the fully seated position.

The sleeve 10 further includes a through slot 19 which is a relativelythinner opening than the open back 17 of sleeve 10. The through slot 19extends longitudinally into sleeve 10 from the wide end 13 of the firstportion 15 of sleeve 10. The through slot 19 terminates part way intothe sleeve 10 in order to maintain the structural integrity of sleeve10. The through slot 19 connects continuously with a partial slot 20which extends the remainder of the length of the sleeve. The partialslot extends only partially into the thickness of sleeve 10 leaving athin connecting portion 6 to maintain the structural integrity of sleeve10. The slots 19 and 20 help give additional flexibility to sleeve 10 toaid in snap fitting the sleeve 10 to rod 1. The through slot 19 andpartial slot 20 also provide additional compressibility to the sleeve toallow the sleeve 10 to be tightly compressed and secured between the rod1 and device 40. The slotted sleeve 10 thus provides a press-fitinterface to secure an attachment device 40 to a rod 1 with the sleevepress-fit therebetween.

The rod, sleeve, and attachment device components of the spinal implantsystem of the present invention may be made of any suitable surgicalgrade material. One such suitable material is a high-grade stainlesssteel, such as 22-13-5 stainless steel.

It is noted that the first taper 11 on the sleeve 10 and the matinginner taper 51 on attachment device 40 may each suitably about a 6degree included taper, providing the necessary force for lockingtherebetween. The second reverse taper 21 on sleeve 10 may be about a 10degree taper. However, these suggested tapers are not intended to belimiting. The diameter of bore 16 of sleeve 10 is suitably and matinglysized to be compressed about a rod 1 having diameter (D). Accordingly,the dimensions and sizes of the various components in this inventivesystem may be any suitable dimensions and sizes which enable thecomponents to have the desired strength as needed, and the desiredfunction as described herein.

While this invention has been described in terms of a particularlyadvantageous embodiment, those skilled in the art can appreciate thatmodifications can be made without departing from the spirit and scope ofthis invention.

We claim:
 1. A spinal implant system including a spinal rod, anattachment device, and an interpositional sleeve for securing theattachment device to the rod, wherein the sleeve has a length andincludes a longitudinal bore therethrough for fitting about the rod andwherein the sleeve includes a first portion and a second portion, andwherein the first portion includes a first outer taper with a first wideend tapering to a first narrow end and the second portion includes asecond outer reverse taper with a second narrow end tapering to a secondwide end wherein the first narrow end of the first taper converges withthe second narrow end of the second taper.
 2. The system of claim 1wherein the first taper and second taper converge at a recessedtransition zone between the first and second tapers.
 3. The system ofclaim 1 wherein the attachment device includes an inner taper having athird wide end tapering to a third narrow end and a counterborepositioned at the third narrow end of the inner taper forming aretaining wall therebetween, such that when the sleeve is positioned andfully seated between the rod and the attachment device, the first outertaper mates with the inner taper of the attachment device and the secondportion of the sleeve mates with the counterbore to secure theattachment device to the rod.
 4. The system of claim 3 wherein thesleeve has an open back extending the length of the sleeve, and whereinthe attachment device has a length and an open back extending the lengthof the attachment device.
 5. The system of claim 4 wherein thecounterbore of the attachment device includes a semicircular bottom wallwhich extends into oppositely located substantially straight widewalls.6. The system of claim 5 wherein the second portion of the sleevecomprises a tapered rounded bottom surface forming the second outerreverse taper and two relief cuts on oppositely located sides of thesecond portion forming two legs extending from the bottom surface. 7.The system of claim 6 wherein the sleeve further includes two retainmenttabs, one extending from each of the legs.
 8. The system of claim 7wherein the open back of the sleeve creates two longitudinal spacedupper edges, and wherein the retainment tabs extend above thelongitudinal upper edges.
 9. The system of claim 8 wherein the open backof the sleeve creates two longitudinal spaced lower edges, one loweredge below each upper edge with a chamfer extending from each lower edgeto a corresponding upper edge, and wherein the distance between thespaced lower edges creates a width therebetween, and wherein the widthis sufficient to enable the sleeve to snap fit laterally onto the rodand laterally retain the sleeve on the rod.
 10. The system of claim 9wherein the rod has a diameter and the width of the open back of thesleeve is slightly smaller than the diameter of the rod, but is largeenough to snap fit laterally onto the rod.
 11. The system of claim 7wherein the retainment tabs of the sleeve each include an abutting tabface to abut against the retaining wall of the counterbore of theattachment device to secure the sleeve in the attachment device and thesleeve and attachment device to the rod.
 12. The system of claim 7wherein the open back of the attachment device creates two upperlongitudinal spaced edges and wherein a means for partially seating thesleeve in the attachment device is provided along the upper longitudinaledges of the attachment device.
 13. The system of claim 12 wherein themeans for partially seating the sleeve includes two oppositely locatedrecessed cuts for accepting the retainment tabs therein.
 14. The systemof claim 13 wherein the retainment tabs each include a tapered leadingedge.
 15. The system of claim 4 wherein the sleeve further includes athrough slot means therein which is a relatively thinner opening thanthe open back of the sleeve, and wherein the through slot means extendslongitudinally into the sleeve from the first wide end of the firstportion of the sleeve and terminates part way into the sleeve tomaintain the structural integrity of the sleeve.
 16. The system of claim15 wherein the through slot means connects continuously with a partialslot means which extends the remainder of the length of the sleeve, andwherein the partial slot means extends only partially into the thicknessof the sleeve leaving a thin connecting portion to maintain thestructural integrity of the sleeve.
 17. The system of claim 3 whereinthe third wide end of the inner taper of the attachment device includesa chamfer extending outwardly therefrom.
 18. The system of claim 1wherein the attachment device has a length and wherein the length of thesleeve is fully contained within the length of the attachment devicewhen the sleeve is fully seated within the attachment device.
 19. Thesystem of claim 1 wherein the sleeve includes an open back providing twolongitudinal spaced sleeve edges, and wherein the sleeve furtherincludes a retainment tab means on each of the spaced sleeve edges forproviding alignment and antirotation of the sleeve in the attachmentdevice.